1. Fields of the Invention
The present invention relates to a bidirectional optical scanner, especially to a bidirectional optical scanner assisting in mammography with improved accuracy of breast cancer diagnosis.
2. Descriptions of Related Art
Breast cancer, the most common cancer in women, caused 500,000 deaths per year worldwide. In western countries, breast cancer afflicts 25 percent of all female cancer patients. According to a medical paper published in Taiwan 2003, breast cancer is the fourth most common cause of female cancer death.
The peak age of breast cancer in oriental women is around 40-50 years old, while that in the western countries is around 30-40. Compared with other cancers, breast cancer is easier to be detected at an early stage. When people feel a lump in the breast, some are reluctant to acknowledge the presence and afraid to have surgery. Thus they tend to delay the treatment. In fact, most breast lumps are benign and many choices are available for the treatment of breast cancer beside removal of the whole breast. In recent clinical practice, the average 10-year disease-free survival rate is 60%. The average 10-year breast cancer survival rate for stage 1 breast cancer with best treatment is 80%. Treatment for stage 0 breast cancer is very successful and the survival rate for stage 0 is nearly 100%. Therefore, early detection and treatment of breast cancer are very important.
Self-examination and doctor's touch are both regular examinations of women's breasts to detect breast cancer earlier. Once abnormal changes are observed, further image analysis is required. The medical ultrasonic Imaging system and mammography are used as diagnostic and screening tools for detecting early breast cancer. They are also used as criterions while making comparison with other breast imaging techniques. In routine examinations, medical ultrasonic Imaging is used for first visit due to the properties of real-time imaging and low cost. As to the mammography, it is a useful screening tool because it detects micro-calcification clusters with high sensitivity and the lesion is detected earlier. Another technique-magnetic resonance imaging (MRI), the widespread of this technique is limited by the high cost of the instrument and the exam. Yet the image resolution of the MRI is higher than the above two techniques and the MRI provides functional imaging.
Like other X-ray tests, mammography uses low-dose ionizing radiation to penetrate the body and create an image. The image is analyzed by radiologists. However, mammography has encountered opposition from the medical professionals due to the high false rate and the radiation does during the test. The false-negative rate of the mammography is at least 10%. The false-negative means a result that appears negative but fails to reveal a condition of having cancer. This is due to dense tissues obscuring the small tumor and the fact that the appearance of cancer on mammograms has a large overlap with the appearance of normal tissues. Some other women are given a false-positive (showing abnormalities, but not cancer) mammogram result.
In order to solve the above problems, there is a need to provide a device assisting in mammography for fewer mammograms and reducing dose exposure.